Details
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Task
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Status: Open (View Workflow)
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Major
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Resolution: Unresolved
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None
Description
MySQL's bug #11745929 fix contains lock_rec_find_set_bit() function optimization:
Author: Jakub Łopuszański <jakub.lopuszanski@oracle.com>
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Date: Mon Jan 31 17:36:48 2022 +0100
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Bug #11745929 CHANGE LOCK PRIORITY SO THAT THE TRANSACTION HOLDING S-LOCK GETS X-LOCK F
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- `lock_rec_find_set_bit` which searches for the first bit set in a bitmap used bit-by-bit loop. Now it uses 13x times faster implementation which tries to skip 64,then 32,16, or 8 bits at a time. This is important for WAITING locks which have just a single bit set, in a bitmap with number of bits equal to the number of records on a page (which can be ~500).
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Port the optimization in MariaDB Server. MariaDB version of InnoDB contains nlz() function, and run-time code contains my_find_first_bit(), which can also be used to optimize the function. See this comment for details.
Attachments
Issue Links
- relates to
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MDEV-34877 Port "Bug #11745929 Change lock priority so that the transaction holding S-lock gets X-lock first" fix from MySQL to MariaDB
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- Closed
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